Lined metal tank with heat shield, indirect fired water heater and method of making same

ABSTRACT

A metallic tank having an insulated interior is disclosed which exhibits unique features to enable the welding of the tank sections together without damage to the insulation. The insulating lining is installed in the multi-piece metallic tank prior to the welding of the tank sections together. A heat shield is provided between the weld area and the insulating liner to prevent damage to the nonmetallic liner during the welding process. The method of assembly allows the economical and rapid fabrication of lined metallic tanks without fear of damaging the lining material. Also, an indirect fired water heater which has a tube heat exchanger in the lined metal tank with the heat shield. The inlet and exit lines of the heat exchanger pass through a bottom plate of the tank. The tank, in such case, contains potable water which is heated by contact with the heat exchanger located within the vessel. Hot boiler water passes through the heat exchanger to heat the water in the vessel. Fittings installed through the top and/or bottom portion of the vessel wall facilitate the drawing off of the heated water and the filling of the vessel with cold water.

This is a continuation-in-part of U.S. application Ser. No. 46,763,filed June 8, 1979, now U.S. Pat. No. 4,241,843.

BACKGROUND OF THIS INVENTION

1. Field of this Invention

This invention relates to lined metallic tanks and methods of makingsame, more particularly those methods involving welding a multi-piecemetallic tank without damaging the nonmetallic lining material, and toindirect fired water heaters, more particularly to such heaters having alined metallic vessel.

2. Prior Art

The tank manufacturing industry has long been plagued with the problemsassociated with forming a multi-piece metallic tank structure having anonmetallic lining on its interior. Since such tanks have achievedwidespread usage in virtually every field, including hot water storagetanks, hot water heating tanks, accumulators for hot water heatingsystems, liquid transportation systems, etc., the problem ofeconomically fabricating such tanks is one of substantial magnitude. Dueto the enclosed nature of such vessels, they are more easily fabricatedin serveral sections which are subsequently welded together. However,when a nonmetallic lining is associated with the tank, the problem ofwelding the tank sections together is magnified, since it must be donewithout destroying the continuity of the interior lining. Any break ordiscontinuity in the lining will result in the eventual contamination ofthe tank's contents and corrosion of the metal tank.

Several attempts have been made to overcome this problem. One solutionhas been to apply the coating to the metal tank after it has been weldedtogether, as exemplified in U.S. Pat. No. 2,758,367. However, thisdrastically limits the types of coating that may be applied to theinterior of a closed vessel. Such a process is also time consuming andexpensive, and there is no assurance that the lining completely coversthe interior of the vessel as intended.

Where a foamed material is utilized as the insulating lining, it may befoamed in situ. This involves the use of an interior and exterior vesselwherein the foam is placed in the space between the two vessels. Theplastic bottle may be considered as an interior vessel but not capableof withstanding any appreciable pressure on its own. (The insulationobtained by foaming in place is different from the design of thisinvention where the foam is formed into the desired shape from aseparate mold.) Processes utilizing these concepts are shown in U.S.Pat. Nos. 3,313,020 and 3,328,496. This process is more expensive sinceit requires the use of two vessels. The foam must also be foamed insmall sections to allow for the complete escape of the gases generatedby the foaming process and, therefore, such method is unduly timeconsuming when fabricating large vessels or tanks.

Another method of fabricating lined, multi-piece metallic vesselsinvolves the use of a chill ring placed in the interior of the metallicvessel adjacent the weld area. The chill ring is usually an annularmetal structure, which may or may not have a coating thereon, and servesto absorb the heat generated by the welding process such that it doesnot destroy the tank lining. But chill rings do not protect the materialinside of the tank directly underneath the chill rings. The use of chillrings are well-known and are shown in U.S. Pat. Nos 2,412,271 and2,970,719. The drawbacks to such system are obvious, insofar as the useof a separate structure increases the cost and weight of the tank whileserving effectively no useful purpose once the tank is welded together.

It is also known to utilize a rubber material as an insulating bandinstalled adjacent to a welding area, as set forth in U.S. Pat. No.2,587,840. However, the purpose of this insulating band is not toprotect the lining of the tank since there is no lining in the areawhich the band is used, but to prevent the current generated by theelectric welding process form jumping to an adjacent metallic wall.Other methods of fabricating welded vessels are set forth in U.S. Pat.Nos. 845,760, 2,113,060, 2,820,427 and 3,253,731. See also U.S. Pat.Nos. 2,542,543, 2,317,734, 1,549,721, 4,099,641, 2,729,313, 2,263,021,2,146,381, 2,551,484, 3,358,118, 3,614,967 and 3,326,141.

Typical prior art hot water heaters comprise a generally cylindricalstorage tank, and heating means to heat the water stored in the tank. Indirect fired water heaters the heating means may take the form of a gasburner located at the base of the cylindrical tank (as shown in U.S.Pat. Nos. 817,589 and 2,187,917) or electrical heating elementsextending into the tank (shown in U.S. Pat. No. 2,303,126). The coldwater usually enters through the top of the tank passing downwardly in atube and exiting near the bottom of the tank. When heated, the waterrises and is drawn off by a hot water exit tube.

Indirect fired water heaters are also known. They differ from theaforementioned directed fired type insofar as the heater water withinthe storage tank is not withdrawn and used, but acts as a heat exchangemedium. Cold water in the storage tank is warmed by a heat exchangerwith the heated water. No direct contact is made with the heating meansor the heated stored water.

Most of the prior art water heaters, whether the direct or the indirecttype, use some form of insulation around the exterior of the tank toprevent undue loss of heat by radiation. Solid flexible insulation isplaced around the tank and retained in position by an outer wall, asshown in U.S. Pat. Nos. 2,303,126 and 2,187,917.

It is also known to make a water storage tank having concentricallyarranged inner and outer tanks with a vacuum insulating spacetherebetween (U.S. Pat. No. 1,327,693). However, such tanks are normallyused only for the storage and not the heating of water, since theinsulating space on the bottom would prevent heat transfer between aburner and the inner tank.

Containers having inner and outer spaced apart walls with an insulatingvacuum therebetween are shown in U.S. Pat. Nos. 1,511,852 and 1,673,653.These containers are used to store a liquid and to prevent transfer ofheat to or from the liquid. See also U.S. Pat. Nos. 999,672, 1,691,912,2,666,979 and 3,123,054.

See further U.S. Pat. Nos. 2,794,570, 3,064,344, 2,787,216, 3,247,999,2,721,580, 2,302,835, 3,132,761, 3,057,509, 2,620,963 and 2,809,762.

BROAD DESCRIPTION OF THIS INVENTION

An object of this invention is to provide a tank and process whichobviates the abovementioned prior art problems. Other objects andadvantages of this invention are set out herein or are obvious herefromto one ordinarily skilled in the art.

The objects and advantages of this invention are set out herein or areobvious therefrom to one ordinarily skilled in the art.

The objects and advantages of this invention are achieved by the tank,heater and processes of this invention.

This invention obviates the problems associated with the aforementionedprior art teachings and provides a method of making a nonmetallic linedmetallic tank that is rapid, economical, and involves no extraneouselements which take up usable space in the tank's interior. The tankaccording to this invention comprises a multipiece metallic outer tank,an insulating liner of foam material (such as urethane foam), and arigid plastic inner tank. The inner nonmetallic liner makes the tankcorrosion resistant. The inner nonmetallic liner can be made of, forexample, plastic (preferred) or rubber. A heatshield of high temperaturesilicone rubber (preferred) or equally resistant material is placedaround the exterior of the insulating liner so as to be located betweenit and the metallic tank, at the location where the metallic outer tanksections are welded together. The urethane foam liner may haveindentations therein to accommodate the heat shield such that the heatshield does not in any way enlarge the requisite dimensions of the tank.It has been found that the high temperature silicone rubber effectivelyinsulated the urethane from the heat generated during the weldingprocess such that the foam is in no way damaged thereby. The hightemperature silicone rubber can be replaced with any equivalent hightemperature resistant material having a low coefficient of heatconductivity or transfer.

To assemble the tank, the two vertically divided halves of the urethanefoam insulation are placed around the one piece inner plastic tank andthis assembly is placed in a first portion of the metallic tank,preferably a lower half. A heat shield, preferably of high temperaturesilicone rubber, is placed around the exterior of the insulating linerin an indentation provided adjacent the welding area. A second metallicportion is then placed over this structure and the metal tank portionsare welded together.

Another embodiment of this invention is directed toward a novelconstruction of an indirect fired water heater. The water heatercomprises the lined metallic vessel of this invention having a heatexchanger (e.g., a finned tube heat exchanger or a smooth-type heatexchanger) disposed therein. Assembly is done in much the same manner asthe heat exchanger fits through the bottom port and is affixed intoplace via attachment of its inlet and outlet tubes (pipes) to (andthrough) the bottom cover plate of the tank. Cold water contained withinthe vessel is heated by hot water circulating through the heatexchanger. The vessel is of multi-piece constructions having upper andlower sections welded together about their circumferences.

The cold water to be heated enters the interior of the vessel viathrough a fitting entending through the bottom wall of the lined vessel.Alternately, the fitting may extend through the bottom plate. After orduring heating, the water can be withdrawn through one or more sililarthrough fittings. The water is heated via hot water passing through theheat exchanger located within the inner vessel. The inlet and outlet forthe heat exchanger extend through the bottom plate covering an openingin the vessel and are connected to a heating device to heat the watercirculating through the heat exchanger.

The lined vessel is provided with insulation means between the outermetallic tank and the inner plastic liner to prevent undue heat loss byradiation and to prevent injury caused by an individual coming intocontact with the heated vessel.

An electrical imersion heater can be attached to the heat exchangerplate to provide for auxillary heating.

DETAILED DESCRIPTION OF THIS INVENTION Brief Description of the Drawings

In the drawings:

FIG. 1 is a side view, partially broken away, of a lined metallic tankaccording to this invention;

FIG. 2 is an exploded, perspective view of the tank of FIG. 1; and

FIG. 3 is a side view, partially broken away, of an indirect fired waterheater according to this invention.

Detailed Description of the Preferred Embodiments

The tank according to this invention is shown in FIG. 1 and comprisesone-piece inner plastic tank 10, foam liner 12 and metallic tank 14.Plastic tank 10 can be made of any rigid or semi-rigid plastic materialdepending, of course, on the type of liquid with which the tank isintended to be used. Metallic tank 14 is shown as being comprised oflower and upper portions 14a and 14b, respectively, divided in ahorizontal plane at its approximate mid-point. This construction,however, is merely for the purposes of illustration and it is understoodthat the tank can be constructed of any number of portions dividedeither horizontally, vertically, or at any other orientation. The lowertank portion is shown as having two connecting means 16 which can beconnected to the system utilized for filling or emptying the tank, or ifthe tank is utilized in a fluid system of any sort, connections 16illustrates the means by which the tank is connected to such system.Metallic tank 14 can be constructed of metal such as steel (preferred),titanium, aluminum, etc. Connecting means 16 communicates with theinterior of plastic tank 10. Nipples 19 of plastic tank 10 fit throughthe lower holes in the foam insulation halves 12c and 12b formed bylower slots 24a and 24b (not shown) therein, respectively, and snugglyfit into and all of the way through connecting means 16. Suffice to saythat it is not critical to the instant invention that the connectingmeans be located in the lower portion of the tank, and it can be locatedin any desired position.

Inner plastic tank 10 most preferably is polyethylene, having athickness of about 60 to 150 mils. Obviously, any other plastic materialor rubber can be used as long as it does not contaminate the water (orother contents) in inner plastic tank 10 and prevents corrosion ofmetallic tank 14 itself. Polyethylene can be used at temperatures up to180° F.

As is illustrated in the Figures, insulating liner 12, which can beurethane foam, or any other foam material depending upon the use ofwhich the tank is subjected, has an indentation 12a about its exteriorperiphery at the location of the juncture of the upper and lower metaltank portions. This is to accommodate heat shield 18, which is in theform of an annular band and is preferably fabricated of high temperaturesilicone rubber. Insulating liner 12 helps to minimize heat loss byradiation. Upper tank portion 14b is shown having two connection means20, which communicate with the interior of plastic tank 10. Nipples 21of plastic tank 10 fit through upper holes in foam insulation halves 12cand 12b formed by upper slots 25a and 25b therein, respectively, andsnuggly fit into and all of the way through connecting means 20. Plate22 is bolted onto the bottom port 23 of tank 10.

To assemble the tank the one-piece inner plastic tank 10 is placedinside of the vertically divided foam insulation halves 12b and 12c andthis assembly is placed into lower tank portion 14a. Although two halves12b and 12c are shown, it is understood that insulating liner 12 can bedivided vertically into several sections to facilitate handling,depending upon the size of the tank to be fabricated. High temperaturesilicone rubber heat shield 18 is then placed in peripheral notch 12a onthe foam liner and fastened in position by any known means. Upper tankportion 14b is then placed over this assembly such that peripheralflange 14c rests on the upper edge of lower tank portion 14a, as shown.The assembly is then welded at the juncture of tank portion 14a and 14bby any known welding means. Heat shield 18 insulates the urethane foam12 and nonmetallic inner tank liner 10 from damage due to the heatgenerated during the welding process. The thusly assembled tank is thenready for use.

Although the assembly method has been described in terms of a verticallyoriented tank, the method according to this invention is equallyapplicable to a horizontally oriented tank. Also, metallic tank 14 canbe divided into more than two sections as described, depending of courseon the dimensions of the finished product.

The nonmetallic lined tank of the invention can be used to store fluids(liquid or gas) and chemical reactions can be conducted therein. Thefully lined (pressurizable) tank can be used as a hot water storagetank, a potable water storage tank, a chlorine holding tank, a solarheat storage tank, a storage tank for potable fluids such as carbonatedbeverages, alcoholic beverages, syrups, pharmaceuticals and the likewhich will not contaminate such fluids, or a tank for storing andtransporting insecticides, fungicides, pesticides and other chemicals.

The indirect fired hot water of this invention is shown in FIG. 3 and isthe same as the tank shown in FIG. 1, except that it further includessmooth-type tube heat exchanger 26. Smooth-type tube heat exchanger 26extends into the interior of nonmetallic tank 10, with inlet pipe 27 andoutlet pipe extending through bottom plate 22 covering bottom opening23. (Tube heat exchanger 24 can be a finned tube heat exchanger, etc.)

Smooth-type tube heat exchanger 26 has inlet tube 27 and outlet tube 28extending externally of bottom plate 22. Inlet tube 27 and outlet tube28 are connected to heater 31 via conduits 29 and 30, respectively,shown diagrammatically in FIG. 3, (extending through the wall of tankstand 32). Heater 31 can be any known apparatus for heating water, suchas, an electric or gas burner. A pump (not shown) can also be used totransfer the hot water from heater 31 and cause it to circulate throughheat exchanger 26 and back to heater 31. No detailed description of thepump or its connection to the circuit is believed to be necessary sincesuch are well within the ordinary level of skill in the art.

Cold water is supplied to nonmetallic tank 10 through one of bottomfittings 16, which connect the interior of plastic tank 10 with externalconduits (not shown) for supplying cold water. The water is drawn offafter it has been heated through one of top fittings 20, which areconnected to external conduits (not shown). Fittings 16 and 20 can havestandard pipe connections on their external end to facilitate connectionwith the aforementioned conduits, etc. Although two top and two bottomfittings are shown, it is understood that any number (e.g., one, three)of such fittings can be used. Bottom fittings 16 can alternately belocated in bottom plate 22.

In operation, the cold water to be heated is pumped into plastic tank 10by standard known pumping means or by city water pressure. Hot water iscaused to circulate through tube heat exchanger 26 thereby transferringits heat to the colder water within the vessel. The water within heatexchanger 26 then returns to heater 31 via conduit 28-30 to be reheated.The water within plastic tank 10, which is now heated, can be withdrawnthrough top fittings 20. Plastic tank 10 prevents contamination of thewater so that it is not rendered unfit for human consumption.

It is understood that the foregoing description of the tank and methodof making it are for illustrative purposes only and that variousmodifications can be made thereto without exceeding the scope of theappended claims.

What is claimed is:
 1. An indirect fired water heater comprising:(a) amulti-section metallic outer tank wherein the sections are weldedtogether; (b) a liner of foam insulating material disposed on theinterior of said multi-section outer tank, said foam insulating linerhaving a smooth interior without any inwardly deformed regions; (c) heatshield means disposed between said outer tank and said foam insulatingliner adjacent the welded junctions of said outer tank to prevent damageto or destruction of said foam insulating liner caused by heat generatedduring the welding operation; (d) said foam insulating liner havingretaining means for securement of said heat shield means adjacent eachwelded junction, said retaining means not inwardly deforming said foaminsulating liner in the region of each welded junction and securing saidheat shield means in position even when said outer tank is not in place;(e) an inner tank of nonmetallic material disposed inside of said foaminsulating liner; (f) means to place water to be heated within saidinner tank and to withdraw same therefrom; and (g) heat exchange meanslocated within said inner tank to transfer heat from a fluid passingtherethrough to said water within said inner tank.
 2. The indirect firedwater heater as claimed in claim 1 wherein said heat shield means is aring made of a high temperature silicone rubber or equivalent hightemperature material which has a low coefficient of heat conductivity.3. The indirect fired water heater as claimed in claim 2 wherein saidfoam insulating liner is made of a urethane foam.
 4. The indirect firedwater heater as claimed in claim 1 wherein said foam insulating liner ismade of a urethane foam.
 5. The indirect fired water heater of claim 1wherein said heat exchange means is of the finned tubing-type or thesmooth tubing-type.
 6. The indirect fired water heater of claim 5wherein there is also means to circulate a heated liquid through saidtube heat exchanger.
 7. The indirect fired water heater of claim 6wherein said heated liquid is water.
 8. The indirect fired water heaterof claim 1 wherein said inner tank is made of a plastic or a rubber. 9.The indirect fired water heater of claim 8 wherein said inner tank ismade of polyethylene.
 10. The indirect fired water heater of claim 8wherein said inner tank has a thickness of about 60 mils to about 150mils.
 11. The indirect fired water heater as claimed in claim 1 whereinsaid retaining means is comprised of an outer peripheral groove locatedin said foam insulating liner, said peripheral groove being locatedalong said welded junction or junctions and in which said heat shieldmeans is disposed.